<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>04-圆的面积</title>
</head>
<body>
    <script>
        // 页面弹出对话框
        let num = prompt('输入园的半径')
        // 计算圆的面积
        let jieguo = 3.14 * (num * num)
        // 页面输出
        document.write(jieguo);
        
    </script>
</body>
</html>